Photos leaked Sunday out of China suggest the country is developing a second stealth fighter that has similarities with both the F-35 Lighting II and the F-22 Raptor. The photos were leaked as U.S. Defense Secretary Leon Panetta is visiting China.

The first photos of a shrouded new airplane showed up in video clips on the Internet in June. It is reportedly being built by Shenyang Aircraft Corporation (SAC), and may be in direct competition with the J-20 airplane being developed by Chengdu Aircraft Corporation (CAC), according to a report in the Wall Street Journal.

The jet's designation is not clear, having been called 'J-21', 'J-31', and 'F-60' on various sites on the Internet. Observers say it appears to be similar in shape and size to the F-35, but also has contours reminiscent of the F-22. The Australian newspaper said that Chinese hackers had been able to mine design data after breaking into a computer system belonging to BAE Systems, which could account for some of the similarities.

The new jet has a twin engine configuration, which could give it a higher takeoff weight than the F-35 ... or it could be indicative of design inefficiencies or a lack of faith in domestic engine design.

Neither the new airplane or the CAC J-20 is beyond the prototype stage, according to the WSJ, and their capabilities are far from being determined. But it is clear that China is working on advanced fighter aircraft, and may have introduced competition in defense contracting into the mix.